PyMuPDF4LLM integration to LangChain (#29953)

## PyMuPDF4LLM integration to LangChain for PDF content extraction in
Markdown format

### Description

[PyMuPDF4LLM](https://github.com/pymupdf/RAG) makes it easier to extract
PDF content in Markdown format, needed for LLM & RAG applications.
(License: GNU Affero General Public License v3.0)


[langchain-pymupdf4llm](https://github.com/lakinduboteju/langchain-pymupdf4llm)
integrates PyMuPDF4LLM to LangChain as a Document Loader.
(License: MIT License)

This pull request introduces the integration of
[PyMuPDF4LLM](https://pymupdf.readthedocs.io/en/latest/pymupdf4llm) into
the LangChain project as an integration package:
[`langchain-pymupdf4llm`](https://github.com/lakinduboteju/langchain-pymupdf4llm).
The most important changes include adding new Jupyter notebooks to
document the integration and updating the package configuration file to
include the new package.

### Documentation:

* `docs/docs/integrations/providers/pymupdf4llm.ipynb`: Added a new
Jupyter notebook to document the integration of `PyMuPDF4LLM` with
LangChain, including installation instructions and class imports.
* `docs/docs/integrations/document_loaders/pymupdf4llm.ipynb`: Added a
new Jupyter notebook to document the usage of `langchain-pymupdf4llm` as
a LangChain integration package in detail.

### Package registration:

* `libs/packages.yml`: Updated the package configuration file to include
the `langchain-pymupdf4llm` package.

### Additional information

* Related to: https://github.com/langchain-ai/langchain/pull/29848

---------

Co-authored-by: Chester Curme <chester.curme@gmail.com>

docs/src/theme/FeatureTables.js

@@ -888,6 +888,13 @@ const FEATURE_TABLES = {
                 api: "Package",
                 apiLink: "https://python.langchain.com/api_reference/community/document_loaders/langchain_community.document_loaders.pdf.PyMuPDFLoader.html"
             },
+            {
+                name: "PyMuPDF4LLM",
+                link: "pymupdf4llm",
+                source: "Load PDF content to Markdown using PyMuPDF4LLM",
+                api: "Package",
+                apiLink: "https://github.com/lakinduboteju/langchain-pymupdf4llm"
+            },
             {
                 name: "PDFMiner",
                 link: "pdfminer",